Misfire when hot

Hello All, on my 95 Taco 2.4L, just changed out, 500 miles ago: head gasket, timing chain, oil pump, fuel injectors, fuel filter, plugs, plug wires, brand new distributor, temp sensor, crank shift position sensor, and spliced in new 4 wire connector supplying power to the new distributor (we had a bad wire in that harness). Compression test for 4 cylinders are between 175-180 psi. 220k miles on the odometer.

Lately, after normal operating temperature, we experience a (CEL) misfire in the #4 cylinder. And after running the truck for an additional 5 minutes, we have a misfire in the #1 cylinder. Pulling the associated #1 & #4 plug wires doesn't affect the rough idle. Pulling #2 or #3 plug wires kills the engine. If we let the truck totally cool down, runs with no problems for a little while, until it all starts over again.

Tried changing out the ignition module, but didn't even start with ebay replacement, so reinstalled old one. Thanks in advance for your thoughts and any assistance.

 

What do the # 2 and 3 plugs look like?

heat related sounds like a coil either ignition or injectors or the ECM

Anything thing that can get hot and cause the circuit to open any connection

Just how was the splice done is it getting hot causing problems it cools down all is good repeat .

Just because parts are new out of the box does not mean they have not failed

Just another thought was this work done for a failed Head Gasket?? Just how much work was done to the head ?

Things get hot a cracked head or even warped enough to drop compression to cause a Miss.

Over the years I have seen some strange things

 

I would measure resistance of the injectors (should be around 12-16 ohms) when it's acting up, sounds like they are going open circuit when they get hot.
If they were "Ebay Specials" I wouldn't be suprised if you got some bad ones.

 

Thanks for your input Wyoming09. I was thinking the same about the ignition coil, but figured it would affect all for cylinders if it were going. I think I will order another set ot injectors. We soldered in the splices for new distributor connector; do you think we should change to crimps? At this point, we are game for anything.

Head gasket job was done because the compression from the #1 cylinder was pressurizing the coolant system. We resurfaced the head, lapped & cleaned valves, new valve seals, measured valve lash.

I really hope its not the ECM, very costly. Thanks again!!!

 

Thank you Dm93. I will perform resistance test. Do I pull the injectors out, heat them up, then test? Or would they fail at ambient? Were would you suggest new injectors from, if not ebay?

Thanks again!

 

If they aren't too bad to get to I would test them on the truck when the missfire is occuring.
I would say rock auto or an auto parts store, why did you change them? Were you having issues prior? Injectors generally don't go bad unless theres fuel contamination, they aren't generally considered a maintenance item.

 

have you checked compression when hot?
Probably not the issue but you might want to recheck your valve clearances, if they are too tight and the valves are leaking when hot you can get misfires.

 

I decided to change the injectors only because they had over 200k miles on them, with no issues (stupid move on my behalf). When misfire occurs again, I shall check compression.

Thanks you all, I really appreciate/need the help!

 

So, it starts and runs well from cold? Check the egr is functioning correctly

 

I would scan and monitor the air/fuel ratio. Sound like it's running lean. I would start with a vacuum leak test, check o2 sensor, MAF sensor, and fuel pressure.

 

truly unsure about ‘ ebay ‘ factor ‘

as much has been done $$$$$ already spent

no doubt its a consideration...........yet why undercut yourself with questionable components

rewiring a distributor is sketchy

good components long run are NOT expensive

 

The engine starts and runs when cold. When reassembling the exhaust system, after head gasket change, we did get an O2 sensor CEL. We cleared it, and the code hasn't returned. I felt that we didn't tighten the bolts enough at the collector (where the exhaust manifold bolts up to the catalytic converter). Well, we didn't tighten the bolts, and the CEL didn't return.

No short term fuel trim data on scan tool. Actually not too much data at all due to OBD I. Might just pull the trigger on name brand injectors.

Thanks for all of your inputs!

 

Scan tool image

 

Where were the injectors from? I’ve had serious issues with eBay/Amazon injectors causing misfires because they’re counterfeit.

intermotor on rock auto or OEM are the only ones I’ve seen work.

 

some parts are as good as OEM ...................in fact on occasion made thr same as the PEM or name brand

some parts are farmed out to the best & used by the OEM

if they can be identified

if U have that verified knowledge

by all means save a little use them

on the other hand to cheap out on ‘ counterfeit ‘ ( a term used a lot on this site ) parts

is pouring a cup of failure/frustration

 

I’ve personally dealt with counterfeit injectors on toyotas it’s a rampant issue on eBay and Amazon. They look legit till you have a known oen next to them

 

This is whats offered on Rockauto (see attached photo). What would you all suggest? For milage on the vehicle, I have a hard time justifying $85 ea. Do you all have any experience with these brands?

Thanks guys!

 

Disregard, just noticed I gotta send my parts in to be serviced. No since on sending counterfeit parts

 

The standard motor is usually a non branded OEM. At least in my experience @CS_AR Can confirm

 

Oops botched his name.. @CS_AR